Thursday, 20 October 2016

Another MPhys publication

In an automatic list of announcements of papers published in the latest edition of Journal of Physics G, I noticed a paper co-authored by one of our (University of Surrey's) MPhys students on her research year placement.  The paper, entitled The PROSPECT physics programme, describes a project taking place at a research reactor at Oak Ridge National Laboratory to study neutrino oscillations.    

Neutrinos are very light elementary particles that are created in nuclear processes such as beta decay.  As far as we currently understand, there are three flavours of neutrino, associated with three different particles:  The electron neutrino, the muon neutrino and the tau neutrino.  When any of these neutrinos are created they are fully of one of these three types.  The oscillations begin as the neutrinos travel through space, and find that they oscillate between the different flavours, so what starts as an electron neutrino will oscillate between the three different flavours.  This effect has been observed by a couple of experiments (Daya Bay and Double Chooz) which both looked at neutrinos as observed at some distance (at least a kilometre) from the nuclear reactors which are the source of the neutrinos.  PROSPECT is designed to look for very short range changes in neutrino flavour by having the detectors very close (a few metres) to the reactors, to help understand the nature of neutrino oscillations, and potentially look for some hypothetical neutrino-like objects. 

The apparatus for the experiment is still being built and tested, and the paper is something of a statement of intent and progress report for the project.  Our student, Brennan Hackett, is working at Oak Ridge National Laboratory on the detector assembly that is being placed close to the High Flux Isotope Reactor (pictured in this post).  Congratulations to Brennan on what I think is your first physics publication (and all while an undergraduate student)!

Monday, 3 October 2016

Seaborg in the Times Crossword

Yesterday, the Times Crossword featured the clue "Old US scientist bags ore for breaking down (7)". Seasoned solvers of cryptic crosswords will spot that "bags ore" has 7 letters, and that "for breaking down" could reasonably indicate that one should make an anagram from the 7 letters.  That leaves the rest of the clue "Old US scientist" as the definition.  The answer is Seaborg

Now, I wouldn't necessarily have thought that Glenn Seaborg was famous enough to feature in a crossword, but with this kind of clue where you have a shortish anagram to work with, it's often the case that you (or at least I) figure out a plausible answer then have to look up to check if you are right.  Seaborg was a nuclear physicist or nuclear chemist (them being really the same thing) who worked at University of California, Berkeley, where he was famous for research into making transuranium elements -- those elements heavier than Uranium which are not found in primordial matter, and need to be synthesised in the lab.  Element number 106 was named after him, as seaborgium.  

Thursday, 22 September 2016

"Until general disarmament has been achieved..."

I moved house a little over a year ago, so naturally many of my things are still in boxes piled up around the place.  Rifling through one of them today, I came across this pamphlet issued by the government in 1963 entitled "Advising the Householder on Protection against Nuclear Attack".  It's pretty sobering reading.

The first line of the introduction reads "The primary purpose of the Government's defence policy is to prevent war; but until general disarmament has been achieved and nuclear weapons brought under international control there still remains some risk of nuclear attack."  I suppose since the time of the publication some progress has been made.  The Partial Test Ban Treaty was signed late in 1963 and the Comprehensive Test Ban Treaty came later.  Still we have not been attacked by nuclear weapons, but "general disarmament" does not seem to be on the cards, except as an accidental side-effect of austerity, perhaps.

Monday, 5 September 2016

Oliver Lodge's Past Years

I'm back from my holidays for the summer now.  Like last year, we ended the school holidays with a week in Deal, in Kent, staying in a friend's house that happens to have a lot of physics–friendly books on the shelf.  I again started reading Oliver Lodge's autobiography, and I got a bit further through it than last time.  It's a bit of a painful read at times, with his bleak assessment of parts of his childhood and schooldays (such as the bullying at school and the violence of the schoolmasters) as well as what seems like a bit of an outsider's career in physics (having started at University late, his not having had the background that leads to it at end of schooling), and the description of his courtship with his to-be-wife sounding very Victorian and somewhat excruciating.  Still, it comes across as a very frank and open description of these sometimes-painful things and so rewarding enough to read.   

I only got about half way through the book during my week there, and not therefore on to the parts of his research career where he was investigating psychic phenomena.  Perhaps that is for the best, but I've made a note this time of how far I got through the book, and maybe next year we will be back and I can pick up from where I left off. 

I've checked, and neither Surrey County library nor the University library have a copy.  I'm not sure I want a copy badly enough to secure one by other means.  I used to use the abebooks website before Amazon took them over, but I'm a little uneasy about giving Amazon money, following widely–reported allegations of unpleasant ways they treat their workers.  Are there any other places one can look, do you know?  

Friday, 26 August 2016

Nuclear in New Brunswick

A quick post today to alert anyone who is looking for a permanent position in nuclear physics and uses my blog as their primary source for information, that Rutgers University is advertising for a tenure track, or potentially more senior, position.  Tell them I sent you :-)

I haven't had the pleasure of visiting Rutgers University, but I do know some of the work they are involved in, thanks to them employing some of our MPhys students for year–long research projects.  Those students have been physically placed at Oak Ridge in Tennessee, though working for Rutgers, helping to develop the Oak Ridge Rutgers University Barrel Array (ORRUBA).  The included in this post is from a talk by Prof. Jolie Cizewski from Rutgers University from a talk at the INPC conference in 2007.  The whole kit has come a long way since then.

Monday, 22 August 2016

Job at UTK

I've had an enjoyable time since coming back from the Nuclear Structure 2016 conference in Tennessee.  I've been for a family holiday in Spain, of the relax-on-the-beach variety.  To be honest, going somewhere hot and lying around not doing much is not my usual idea of a good time, but with two kids, "not doing much" is not an option, and I spent a lot of time in the sea or the pool, playing with them.  Anyway.  Tennessee has cropped up again and prompted me to post:  I received an email this morning saying that there is a post-doc position available in Knoxville.  As someone who once held a post-doc position at the University of Tennessee, Knoxville, I can heartily recommend it as a place to spend a few years.  In fact, downtown Knoxville is considerably more fun that it was 20 years ago when I lived there.  Here's the job advert.  

Since I always like to put a picture on each post, I attach a photo from the one day in the beach holiday when we went on a day trip to do some sight-seeing -- to Girona.

Thursday, 28 July 2016

Nuclear Structure Day 3

This morning's run
It's more than half way through the Nuclear Structure 2016 conference.  Thanks to Kelly's comment on my previous post, I indeed took a run straight down Walnut Street to the river so that I could run along the "Greenway" path that runs alongside it.  I was a bit worried by the very steep hill I ran down to get to the bridge across the main road and then the stairs down to get to the riverside.  It meant that there would be a lot of uphill on the return run, and of course so there was.  I ended up running 2km, so no great shakes, but I certainly felt like I got a lot of exercise while doing it.  

There have been a lot of good talks at this conference.  I particularly enjoyed Gaute Hagen's talk yesterday which showed some recent results from his group's calculations using the coupled cluster method to calculate the properties of the doubly-magic 48Ca nucleus.  They use interactions from chiral effective field theory which one can think of as a fairly fundamental way of describing the nucleon-nucleon (NN) interaction (though it turns out that they are still a little uncontrolled so that there are many such interactions they can choose from) and the whole method falls under the name ab initio, meaning really that they use free NN interactions rather than in-medium interactions to produce the structure of nuclei.  I think there is still some work to make NN interactions sufficiently fundamental to justify the ab initio moniker. But okay, they are heroic calculations that were justifiably published in Nature Physics.  It was good, I think, that they made some effort to get the radius of their nuclei right.  The radius always seems to take second place to binding energy when people are trying to reproduce the properties of nuclei with their theories.  There are strong links between the neutron-proton radius difference and e.g. the expected properties of neutron stars, linked via the equation of state of nuclear matter.  Anyway, the result Gaute presented suggest that the neutron skin is on the lower end of what is usually predicted, which is certainly an interesting result, and I (and many others) await the CREX experiment which is planned to make the best ever measurement of the neutron radius.  The proton radius is relatively easy to measure via electron scattering.

charge radii
The radii of nuclei in this region show really interesting behaviour, as shown by Kei Minamisono in the talk before Gaute's, and by Ronald Garcia-Ruiz's talk immediately after Gaute's.  The second picture here shows a snapshot I took during Kei's talk.  If you click on it you get a slightly bigger version.  The points show the charge radius – so the proton distribution, basically.  The black triangles (second line from top) are for calcium, in which there are always 20 protons.  The radius, between neutron number 20 and 28, shows a kind of inverted parabola with odd-even staggering.  Very few theories can reproduce this.  Then there is a strong linear increase after the N=28 magic number.  Add one proton for scandium, or subtract one for potassium and the details don't just mirror calcium shifted up or down a bit, but look quite different.  There are rich structure effects going on in here that I don' think we fully understand.  Certainly there are approaches (such as density functional theory) which have reproducing radii well within their remit, but simply don't get the details right.

Lee Evitts
Yesterday also saw a Surrey PhD student (who spends all his time actually working at the TRIUMF lab in Canada despite formally being enrolled at Surrey) who is also a graduate of our MPhys programme, Lee Evitts, give a talk to the couple of hundred delegates present.  He did a good job, talking about his results of spin-zero excited states in nickel isotopes, and what they tell us about the nature of those nuclei.  In particular he was looking at electromagnetic transitions between spin-zero states, which are very peculiar as they cannot proceed by the emission of a gamma–ray photon, which is the usual way that electromagnetic transitions proceed.  This makes the experiments harder as the probes tend to be messier.  Lee's experiment used proton scattering off of the nuclei to let the associated Coulomb field cause the transition to take place.